Mérida was founded by the Romans in 25 B.C., under the name of Augusta Emerita, as a colony for veterans of the Vth and Xth Legions. The town prospered and became capital of the province of Lusitania; with a population of 50,000, it was the largest Roman town in Iberia and the political and cultural center of the whole peninsula. After Christianity was adopted as the state religion of the Roman Empire Mérida was one of the first Roman cities to become the see of an archbishop. It retained its position after its conquest by the Visigoths in the fifth century, but its decline began after it fell to the Moors in 713. The decline continued after its reconquest by Alfonso IX of León, who granted it in 1229 to the knightly Order of Santiago.
Along the railroad line is the massive Acueducto de los Milagros, a Roman aqueduct, built of granite and brick, of which there survive 37 piers and 10 arches up to three stories high. It brought water to Mérida from the Prosérpina reservoir 10km/6mi away.
On the west side of the Alcazaba is one of Mérida's principal sights, the Roman bridge over the Guadiana, probably built in the reign of Augustus but frequently renovated or rebuilt in later centuries. With 64 granite arches, it has a total length of 792m/866yd.
Mérida, the Spanish town which is richest in remains of the Roman period, lies on a flat-topped hill on the right bank of the Río Guadiana, on the sparsely populated plateau of Extremadura which adjoins the Portuguese frontier.
Adjoining the site of the hippodrome, on the far side of Calle Teniente Coronel Yagüe, can be seen the 140 arches of the Acueducto Moderno, the "modern" aqueduct built by the Moors.
South of the Plaza de España, on the banks of the Guadiana, is the Alcazaba, a Moorish castle created in 855 by the enlargement of an earlier Roman and Visigothic building, which was later converted by the Order of Santiago into a monastery. The Moors restored the Roman cistern in the basement of the fortress and built a flight of steps down to it, re-using Roman and Visigothic stones.
Address: Mérida Alcazaba, Plaza de España, Merida , Spain
Adjoining the theater are the excavated remains of the Roman Amphitheater, built in 8 B.C., in which 15,000 spectators could watch gladiatorial contests. The amphitheater could be flooded, so that ships could sail in and naval battles could be fought. After gladiatorial contests were banned material from the amphitheater was used for repairing the bridge over the Guadiana.
A little way north of the Plaza de España, at the junction of two streets, the Arco de Trajano or Arco de Santiago, is a Roman triumphal arch almost 13m/43ft high, with four rows of columns, which was the north gate of the Roman town.
To the right of the Termas is the Casa Romana, a Roman villa of the A.D. first century with remains of wall painting and very beautiful pavement mosaics.
From the Alcazaba, Calle de Oviedo runs south to the Plaza de Toros (Bullring), beyond which is the Casa del Mithraeo, a large Roman villa named after a mithraeum which was found here, with very fine mosaics depicting the origin of the world.
Northwest of the amphitheater, beyond the railroad, are the remains of a hippodrome, the only one of its kind in Spain. The site is now much overgrown.
From the Acueducto Moderno the Avenida Extremadura runs along the railroad to the station, just before which stands the church of Santa Eulalia, built in the fourth Century on the site of a Roman temple and completely rebuilt in the 13th century.
The hub of the town's traffic is the arcaded Plaza de España, at the northwest corner of which stands the church of Santa María la Mayor (13th-15th C.). It was founded by Alonso de Cárdenas, Grand Master of the Order of Santiago, who is buried in the church along with his wife.
To the west of the Plaza de España, at the corner of Calle Romero Leal Sagasta, is the Temple of Diana (not in fact dedicated to Diana but to some unknown cult), which was converted into a noble mansion in the 16th century.